Nigeria and several of its African neighbors call the kidnapping of more than 200 schoolgirls by Boko Haram militants "a heinous example of the scourge of sexual violence."

Officials from Benin, Cameroon, Chad, and Niger joined Nigeria on the sidelines of a global summit in London on ending sexual violence in war.

Conference co-host Angela Jolie said it's a myth that rape is inevitable during war. The actress, a special envoy of the United Nations High Commissioner for Refugees, called rape another weapon used to torture and humiliate.

British Foreign Secretary William Hague, who also hosted the summit, said participants aim to "shatter the culture of impunity" of sexual violence. He added that few of the guilty are punished.

Hague promised more British help in the search for the kidnapped Nigerian girls. He said Britain wants to make sure Boko Haram fails in what he calls its "twisted mission" to deny girls an education.